There were several variations over the years but all the boats had hulls that conformed to a design by George Lennox Watson, the RNLI's naval architect from 1887 until his death in 1904.

The majority of lifeboats in service with the RNLI during the second half of the nineteenth century were of the Peake self-righting type, designed to operate in rough seas close to the shore.

Watson designed a new non self-righting hull shape for the RNLB Edith and Annie which was built in 1888.

The engines in the early motor types were regarded almost as an auxiliary and the boats, which had an open deck with end boxes, retained sails and oars.

The boats resembled scaled down versions of the contemporary 45 ft 6 in design, with a small shelter ahead of the aft cockpit and the exhaust funnel in front of it.

All were built by J. Samuel White at Cowes and were powered by a 50 bhp Weyburn CE4 4-cylinder petrol engine driving a single screw.

These were the first twin-engined medium-sized boats intended for stations unable to accommodate the larger types.

4 of the first 5 had petrol engines; the fourth was the first new build diesel-engined lifeboat for the RNLI and the remainder followed suit.

28 boats were built, not including 2 destroyed whilst under construction in an air raid on Groves & Guttridge's yard at Cowes.

The first 5 resembled the pre-war 46 ft type but from 1948 a major redesign resulted in a new superstructure with midships steering and a large cabin aft.

The final incarnation of the design, the 47ft Watson-class of 1955, was the last non self-righting class built for the RNLI other than the three 70 ft (21 m) Clyde-class cruising boats in 1965 and 1974.